A regular book passes its information from its author to its readers. There are several disadvantages. First, a regular book cannot adopt itself to serve the different needs of many readers. Before an author starts writing a book, usually the author has to figure out his or her target audience. If the target audience is too small, then many people could not be interested in the book, and therefore the selling volume for the book will become a problem. If the target audience is too large, then the author could have difficulty to present information effectively, and therefore the communication effectiveness will become a problem. Different readers usually have different requirements on how to organize information and how to present information. Sometimes these requirements can contradict each other. To meet the needs of different readers, though an author could show information in many different ways in a same book, the book will then become very tedious, and therefore a reader will have difficulty to access particular information. Due to these limitations, an author usually has to compromise the demands from the readers under different categories. The author can target at several major categories and illustrate information in several ways with each suitable to one of the selected categories. In this way, though the book may look dull, the author could be able to handle the requirements from the reader of several targeted categories. However, the author is still unable to treat each reader individually. It is reader's responsibility to skip unwanted information, locate related information, and digest information. How effective a reader can read a book solely depends on the description in the book as well as the reading skill and the comprehension capability of the reader.
Second, a regular book cannot adopt itself to meet the different requirements of a same user during different stages of reading the book. A reader may require a book to organize and present information differently when the reader reads the book for the first time from when the reader reads the book for the second time, from when the reader reads the books for the third time, and from when the reader reviews the book. Though an author could make different presentations for same information in a same book, the book can then become very unnecessary long, and therefore a reader may have difficulty to locate interesting information. Again, it is the reader's task to locate related information, to look at an issue from different view of point, and to organize the information.
Third, the information flow on a regular book is in one direction. A regular book passes information from its author to its reader, but not from its reader to its author. When a reader has a problem in reading a regular book, the book does not provide a mechanism for the reader to ask the author a question and for the author to present information differently
For the above reasons, it is desirable to create a system for helping a reader to access information efficiently and helping an author to present information effectively.